Multiplexer

A multiplexer comprising:

• a common connection terminal;
• and
• a transmitting filter and a receiving filter connected in common to the common connection terminal;
• wherein
• the transmitting filter and the receiving filter each include a resonator;
• the resonator of the transmitting filter and the resonator of the receiving filter share a piezoelectric substrate;
• the resonator located closest to the common connection terminal in terms of a circuit configuration of the transmitting filter defines a series-arm resonator;
• the resonator located closest to the common connection terminal in terms of a circuit configuration of the receiving filter defines a longitudinally coupled resonator acoustic wave filter;
• the series-arm resonator of the transmitting filter includes an IDT electrode including a plurality of electrode fingers;
• the longitudinally coupled resonator acoustic wave filter of the receiving filter includes a plurality of IDT electrodes each including a plurality of electrode fingers;
• in each of the IDT electrodes of the longitudinally coupled resonator acoustic wave filter and the series-arm resonator, when a direction in which the plurality of electrode fingers extends is denoted as an electrode finger extension direction and a direction orthogonal or substantially orthogonal to the electrode finger extension direction is denoted as an electrode finger orthogonal direction, a region where the plurality of electrode fingers adjacent to each other in the electrode finger orthogonal direction overlap is a crossover region, and a dimension of the crossover region along the electrode finger extension direction is a crossover width;
• and
• when in the transmitting filter, a product of a number of the plurality of electrode fingers of the IDT electrode of the series-arm resonator and the crossover width is denoted as C1, and in the receiving filter, when a total value of a product of the number of the plurality of electrode fingers of each of the plurality of IDT electrodes of the longitudinally coupled resonator acoustic wave filter and the crossover width is denoted as TC2, TC2<C1.